1. Field of the Invention
The present invention relates to utilizing mechanical refrigeration, and more particularly to a system for transmitting and storing cold medium, preferably underground, for effective uses during summer seasons. This system is called WISER, meaning Winter Ice For Summer Energy Relief.
2. Description of the Prior Art
Prior art ground cold storage systems are generally accomplished by blowing winter cold ambient air through a cold reservoir formed by a bed of crushed stones and rock. In other cases, cold liquid medium is pumped through pipes embedded in stone and rock medium in the form of which constitutes a closed heat-exchange system.
The stones and rocks, as a cold storage reservoir, have several shortcomings. First, cold storage capacities are limited because of the narrow temperature range for cooling. In other words, the difference of storage temperature in winter and upper-limit useful temperatures in summer is less than thirty degrees Fahrenheit (30.degree. F. to 60.degree. F). For example, in a volume of one cubic foot of stone at a temperature difference of 30.degree. F., the energy flux is about 1.3.times.10.sup.3 BTU. Assuming a summer requirement of 25.times.10.sup.6 for an average size home, a volume of cold storage required for cooling is estimated at 20.times.10.sup.3 cubic feet. In contrast to this large volume, if ice is used for cold storage instead of rock, the required storage volume is about 2.5.times.10.sup.3 cubic feet.
Another shortcoming of the stone and rocks as cold storage is the low thermal conductivity. It would require a long length of liquid pipes and considerable pumping power in order to meet the maximum cooling rate required during hot summer days.
Furthermore, the ground cold storage systems mentioned above can be only applied to regions where sufficient freezing climate exists.